The present invention relates to a method recognizing a character pattern or the like in an optical pattern reader.
There are generally two ways of reading a character pattern or the like on a sheet through the use of an optical pattern reader (referred to as "OCR" hereinafter): one where a character pattern is read and recognized with certain limits placed thereupon to simplify recognition logic; and the other where a limit-free or constraint-free character pattern such as a freely written character is read and recognized which suffers from the complexity of recognition logic to some extent.
The concern of the present invention is directed to the latter, namely, a way of recognizing a constraint-free handwritten character. The conventional approaches for recognition of such, handwritten characters are by a feature extraction method. According to the prior art feature extraction method, a character pattern is divided into a predetermined number of segments in line with a basic pattern standard which reflects features of a specific pattern well. Each of the segments is called a picture element. In order that features of a pattern with diversity like a handwritten character can be extracted and thus extracted features be made adapted to some of the picture elements, all combinations of the features ranging from ones of the highest probability of the appearance to ones of the lowest probability should be written into a dictionary area within a system memory together with correlation information between combinations of the features and character patterns. To make recognition of a handwritten character possible necessitates a bulky look-up table in the dictionary area, a system memory of extremely large capacity, a lot of time for retrieval of the dictionary area, and the pursuit of two dimensional pattern features. These parameters make recognition logic and a reading out scheme complicated and present a severe problem with practical use of the OCR.
Another problem is that an attempt to minimize reading error will cause an increase in a rejection or failure rate and an attempt to minimize the rejection rate, on the other hand, will cause an increase in the probability of reading error because the look-up table in the dictionary area is too complicated.